JP2023012683A - Method for calibrating measurement device for subsurface exploration - Google Patents

Abstract

To provide a method for calibrating a measurement device for subsurface exploration, which can facilitate calibration by using components used in subsurface exploration or simple jigs.SOLUTION: The present invention is a method for calibrating a measurement device for subsurface exploration mounted to a penetration tester for penetrating a rod into the ground when exploring a target subsurface. The method comprises: installing a first calibration plate on a pedestal part so as to block a route through which the rod passes (step S2); contacting the tip of the rod with the first calibration plate (step S4); loading the rod with a known load based on a weight part and a vibrator and performing measurement by a load measurement unit of the measurement device for subsurface exploration (steps S5, S6); and performing calibration based on the measurement result of the load measurement unit and the known load (step S7).SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a method for calibrating a measuring device for ground survey, which is attached to a penetration tester for penetrating a rod into the ground when surveying a target ground.

In conventional general ground surveys, ground constants related to ground strength are obtained by in-situ tests such as Swedish sounding (SWS) tests in the case of small-scale buildings. The soil constant is used to examine the soil's bearing capacity against long-term loads.

The SWS test is a survey method that evaluates the hardness and softness of the ground by the penetration resistance of a rod with a weight attached.In recent years, the ground investigation equipment used for this test has been automated, and even the loading and unloading of the weight, rotation control, and measurement are possible. Automated equipment is also prevalent.

On the other hand, the SWS test reveals the penetration resistance, and there are many problems with its accuracy. Patent Document 1 proposes a method of obtaining highly accurate information by using a penetration tester and applying vibration to it. are doing.

Here, as in the method disclosed in Patent Document 1, when trying to confirm the dynamic penetration amount and load by applying vibration with a vibration exciter using the penetration tester for the SWS test as it is. However, if a displacement meter or load meter is directly attached to the main body of the device, there is a problem that the vibration is large and may affect the accuracy and durability.

Therefore, in Patent Document 2, by attaching a displacement gauge or the like as a simple attachment in the middle of the rod, it is possible to support a wide variety of survey devices and to develop a ground survey measuring device that can perform simple and highly accurate measurements. is suggesting.

JP 2018-17112 A JP 2019-178490 A

By the way, as the load measuring unit of the measuring device for ground investigation, there is a case where, for example, a load meter is used for measuring by providing a jig having a load cell or a strain gauge attached to the impact portion. A potentiometer-type or laser-type displacement gauge, which is a precision machine, may be used as the displacement measurement unit of the ground investigation measuring device.

All of the ground survey measuring devices used in this ground survey method are subjected to a large load due to vibration, so when used repeatedly, periodic calibration is required to ensure accuracy. . However, the work is generally complicated.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method for calibrating a measuring device for ground survey, which can be easily calibrated by using parts and simple jigs used for ground survey.

In order to achieve the above object, a method for calibrating a measuring device for ground investigation of the present invention is a method for calibrating a measuring device for ground investigation that is attached to a penetration tester that penetrates a rod into the ground when investigating a target ground. The penetration tester includes a pedestal portion having an opening for penetrating the rod into the target ground, and a weight portion and a vibrator for applying a load to the upper end of the rod, placing a first calibration plate on the pedestal so as to block at least a path through which the rod passes through the open portion; bringing the tip of the rod into contact with the first calibration plate; A step of loading a known load based on the weight portion and the vibrator, measuring by the load measuring unit of the measuring device for ground survey, and based on the measurement result of the load measuring unit and the known load and a step of calibrating by

In addition, another invention of a calibration method for a measuring device for ground investigation is a calibration method for a measuring device for ground investigation attached to a penetration tester for penetrating a rod into the ground when investigating a target ground, The testing machine includes a pedestal having an opening for penetrating the rod into the target ground, and a first calibration plate attached to the pedestal so as to block at least a path through which the rod passes through the opening. , the step of contacting the tip of the rod with the first calibration plate, and the displacement measurement unit of the ground survey measuring device using the upper surface of the first calibration plate as a reference for measurement. placing a second calibration plate having a known thickness on the first calibration plate; and performing measurement with the displacement measuring unit using the upper surface of the second calibration plate as a reference. and performing calibration based on the measurement result of the displacement measuring unit and the thickness of the second calibration plate.

In the method for calibrating the measuring device for ground investigation of the present invention configured in this way, a known load based on the weight and vibration generator of the penetration tester is loaded on the rod, and the measurement result of the load measuring unit at that time Based on this, calibrate the load measuring unit.

In this way, simply using parts such as the weight and vibrator of the penetration tester used for ground investigation, and a simple plate-shaped jig that can be installed on the pedestal of the penetration tester, can be easily performed. Calibration can be done.

In another method for calibrating a ground investigation measuring device of the present invention, the first calibration plate is installed on the pedestal portion of the penetration tester, and the thickness is known after performing measurement by the first displacement measurement unit. The second calibration plate is placed on the first calibration plate, and measurement is performed again by the displacement measuring unit. Then, the displacement measuring unit is calibrated based on the measurement results of the displacement measuring unit twice.

In this way, calibration can be easily performed simply by installing a simple plate-shaped first calibration plate and a second calibration plate on the pedestal of the penetration tester and performing measurement by the displacement measurement unit. can.

It is a flowchart explaining the flow of processing of the calibration method of the measuring device for ground investigation of the present embodiment. It is a schematic diagram for demonstrating the calibrating method of the load measuring part of the measuring device for ground surveys. BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view explaining an example of a structure of the measuring device for ground surveys. 4 is a flow chart for explaining the flow of processing of a method for calibrating the measuring device for ground survey according to the first embodiment; It is explanatory drawing which showed the process of measuring the plate for a 1st calibration in the calibration method of the displacement measuring part of the measuring device for ground surveys. It is explanatory drawing which showed the process of measuring the plate for a 2nd calibration in the calibration method of the displacement measuring part of the measuring device for ground surveys.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a flow chart for explaining the flow of processing of a method for calibrating a measuring device for ground survey according to the present embodiment. Moreover, FIG. 2 is a figure for demonstrating the calibration method of the load measuring part of the measuring device for ground surveys.

A ground survey using the ground survey apparatus 1 described in the present embodiment is carried out on a survey target ground G for constructing a building such as a house. A ground investigation such as a penetration test is usually directly conducted at one or a plurality of points on the target ground G to be investigated.

For example, in the case of small-scale buildings, a Swedish sounding test (SWS test) is generally performed at one or more points on the target ground G to be investigated. The Swedish sounding test is a type of static penetration test specified in JIS A 1221, and is a ground survey method that estimates the hardness of the ground from the penetration resistance of the rod when screwing the screw point into the ground.

Penetration test machine 2, as shown in FIG. Mainly composed of The base machine 21 is a Swedish sounding tester that has a proven track record in ground surveys of small-scale buildings.

On the other hand, the weight 25 is used to load the screw points in stages used during the Swedish sounding (SWS) test. It has a weight 25 with a total weight of 100 kg according to the standard.

The SWS test basically evaluates the survey results in units of 25 cm. The rod 22 is configured by connecting unit rods 221 of 1 m or 50 cm. That is, the measurement proceeds while adding unit rods 221 .

By attaching the exciter 3 to the penetration tester 2 and applying vibration and impact, it becomes possible to evaluate the support performance and rigidity of the ground more accurately than the Swedish sounding test. In order to evaluate the support performance of the ground, accurate measurement data of the applied load and the amount of penetration are required.

That is, it is necessary to accurately measure the dynamic penetration amount and the load under the condition that the vibrator 3 strikes. This measurement can be performed using a measuring device for ground investigation such as a displacement meter and a load meter originally provided in the penetration tester 2 .

Further, as described below, by attaching a strain amount detector or a displacement meter to a short rod or jig interposed in the rod 22, a ground investigation measuring device having a load measuring unit and a displacement measuring unit can be obtained. can also

For example, in the ground investigation apparatus 1, as shown in FIG. An example of the measuring device 4 is shown in FIG.

This measuring device 4 is mainly composed of a short rod 41 interposed in the rod 22, a strain gauge 42 attached to the short rod 41 as a strain amount detector of the load measuring section, and a non-contact displacement gauge 43 serving as a displacement measuring section. configured to

The short rod 41 is formed of a cylindrical tube having a diameter similar to that of the rod 22, and has an upper connection screw 411 at its upper end and a lower connection screw 412 at its lower end. That is, the short rod 41 interposed between the unit rods 221, 221 has an upper connection screw 411 for connection to the lower end of the upper unit rod 221 and a lower connection screw for connection to the upper end of the lower unit rod 221. 412 are provided.

The strain gauge 42 is attached to the outer peripheral surface 413 of the short rod 41 . The expansion/contraction direction (measurement direction) of the strain gauge 42 coincides with the axial direction of the short rod 41 . A plurality of strain gauges 42 are attached to the outer peripheral surface 413 of the short rod 41 . For example, a pair of strain gauges 42 can be attached every 180° in the circumferential direction. Also, four strain gauges 42 can be attached every 90° in the circumferential direction.

The strain gauge 42 is generally used as a measuring instrument and can be obtained at a very low cost. Moreover, since it can be installed only by sticking it to the outer peripheral surface 413 of the short rod 41, it can be made very compact.

Since the material (Young's modulus E) and cross-sectional area A of the short rod 41 are specified, the axial load N can be easily obtained. where σ is the degree of stress in the axial direction (σ=N/A). The strain ε is a value measured by the strain gauge 42 and corresponds to the ratio of the displacement amount ΔL when the load N is applied to the total length L (ε=ΔL/L).

On the other hand, the non-contact displacement meter 43 is provided so as to measure displacement between a predetermined position of the short rod 41 and a corresponding reference point existing in the vertical direction. Specifically, the relative displacement between the projecting portion 44 projecting from the outer peripheral surface 413 of the short rod 41 and the upper surface 241 (reference point) of the pedestal portion 24 of the penetration tester 2 is measured. .

The non-contact displacement gauge 43 attached to the lower surface of the projecting portion 44 projecting perpendicularly to the outer peripheral surface 413 of the short rod 41 is a laser displacement gauge equipped with a laser S irradiation portion and a light receiving portion. be. The laser S irradiated from the irradiation part of the non-contact displacement meter 43 directed vertically downward is reflected by the upper surface 241 of the base part 24 of the penetration tester 2 as a reflection point and detected by the light receiving part.

The measuring device 4 includes an arithmetic processing section that calculates the load N from the strain amount (ε) detected by the strain gauge 42 . Further, from the detection signal detected by the non-contact displacement meter 43, the displacement (penetration amount) when the load N is applied can be calculated. Since the permissible bearing capacity and the estimated subsidence amount can be calculated from the load and penetration amount thus measured, it becomes possible to evaluate the bearing performance of the ground.

Since the measuring device 4 configured in this manner is used in a state where vibration is continuously applied by the exciter 3, the load due to the vibration is large, and in the case of repeated use, the accuracy is ensured. Therefore, periodic calibration is required.

Therefore, the process flow of the method for calibrating the measuring device for ground investigation according to the present embodiment will be described with reference to the flowchart shown in FIG.
First, in step S1, as shown in FIG. 2, the penetration tester 2 is installed. This installation location does not necessarily have to be on the target ground G.

Subsequently, in step S<b>2 , the first calibration plate 5 is installed on the upper surface 241 of the base portion 24 of the penetration tester 2 . The pedestal portion 24 of the penetration tester 2 is provided with an open portion such as a hole or gap for allowing the rod 22 to pass through and penetrate into the target ground G.

Therefore, if the rod 22 is lowered in the same manner as during the test, the tip of the rod 22 will pass through this open portion. 5 is installed on the upper surface 241 of the pedestal portion 24 .

The first calibration plate 5 is made of a material and has a thickness that can withstand the total weight of the vibrator 3 and the weight portion 25 . The penetration tester 2 for the SWS test is equipped with a weight 25 with a total weight of 100 kg according to the standard. Also, the weight of the exciter 3 is known. In order to use the weight of the weight portion 25 and the weight of the vibrator 3 as a load for calibration, a plate-like member that can withstand the load is used for the first calibration plate 5 .

In step S<b>3 , the rod 22 with the measuring device 4 interposed between the unit rods 221 , 221 is set in the penetration tester 2 . As a result, the strain gauge 42 as the load measuring section is connected to the rod 22 .

Then, in step S<b>4 , the tip of the rod 22 is lowered to contact the upper surface 51 of the first calibration plate 5 . FIG. 2 shows this state. In short, the first calibration plate 5 is brought into a state in which the rod 22 can be supported. While the rod 22 is fixed by the chuck of the penetration tester 2, no load acts on the rod 22 and no load is measured by the load measuring unit.

In this state, in step S5, the weight of the weight portion 25 and the weight of the vibrator 3 is applied to the upper end of the rod 22 as a load by releasing the chuck of the penetration tester 2 . Here, since the weights of the weight portion 25 and the vibration generator 3 are known in advance, they can be said to be known loads.

The weight of the weight 25 (total of 100 kg) and the weight of the exciter 3 can be applied entirely to the rod 22, or any known weight can be applied. In short, among the weights of the parts originally provided in the penetration tester 2, a part whose size to be loaded is known is used as the load.

In step S6, the load value (strain ε) detected by the strain gauge 42 is measured from the no-load state to the time when a known load set by the weight of the weight portion 25 and the weight of the vibration generator 3 is applied. do. The amount of strain detected in this manner is the measurement result of the load based on the weight section 25 and the vibration generator 3 by the load measuring section.

Therefore, in step S7, the load is adjusted so that the load N calculated by the arithmetic processing unit from the strain amount detected by the strain gauge 42 has the same magnitude as the known load based on the weight 25 and the exciter 3. Calibrate the measurement unit.

Next, the operation of the method for calibrating the measuring device for ground survey according to the present embodiment will be described.
In the method for calibrating the ground investigation measuring device of the present embodiment configured in this way, a known load based on the weight portion 25 and the vibration generator 3 of the penetration tester 2 is loaded on the rod 22, and the load at that time The load measuring section is calibrated based on the measurement result of the strain gauge 42, which is the strain amount detector of the measuring section.

In this way, parts such as the weight portion 25 and the vibration generator 3 of the penetration tester 2 used for ground investigation, and a plate-shaped simple first calibration plate that is only installed on the pedestal portion 24 of the penetration tester 2 5, calibration can be easily performed. For this reason, it is possible to repeatedly perform calibration at an arbitrary timing such as before or during the test, so that it is possible to efficiently perform highly accurate measurement.

Example 1, which is different from the above-described embodiment, will be described below with reference to FIGS. 4 to 6. FIG. It should be noted that the same terminology or the same reference numerals will be used to describe the same or equivalent portions as those described in the above embodiment.

In the above-described embodiment, the method for calibrating the load measuring unit of the measuring device for ground investigation has been described. In the first embodiment, a method for calibrating the displacement measuring unit of the ground investigation measuring device will be described. Specifically, the non-contact displacement gauge 43 of the measuring device 4 described in the above embodiment will be used for description.

In the method for calibrating the non-contact displacement gauge 43 of the first embodiment, two plate members are used. As the first plate, the first calibration plate 5 described in the above embodiment can be used. However, in the method for calibrating the non-contact displacement meter 43, no load is applied to the plate-like member, so another plate-like member can be used.

A second plate-like member is referred to as a second calibration plate 6 . The second calibration plate 6 is a plate-like member with a known thickness. Both the first calibration plate 5 and the second calibration plate 6 are installed so as to block at least the path through which the rod 22 passes in the open portion of the pedestal portion 24 .

Also, the first calibration plate 5 and the second calibration plate 6 are formed to have a width that can cover at least the point through which the rod 22 passes to the reflection point of the laser S of the non-contact displacement gauge 43 . Furthermore, the first calibration plate 5 and the second calibration plate 6 are formed with a constant thickness over the entire area.

A hole 62 is drilled in the second calibration plate 6 at a position corresponding to the path through which the rod 22 passes, as shown in FIG. This hole 62 is formed, for example, one size larger than the diameter of the rod 22 so that the tip of the rod 22 which is easily lowered can pass therethrough.

Subsequently, the flow of processing of the method for calibrating the measuring device for ground survey according to the first embodiment will be described with reference to the flowchart shown in FIG.
First, in step S11, as shown in FIG. 5, the penetration tester 2 is installed. This installation location does not necessarily have to be on the target ground G.

Subsequently, in step S<b>12 , the first calibration plate 5 is installed on the upper surface 241 of the pedestal 24 of the penetration tester 2 . Then, similarly to the test, the rod 22 is lowered to bring the tip of the rod 22 into contact with the upper surface 51 of the first calibration plate 5 (step S13).

Subsequently, in step S<b>14 , the non-contact displacement gauge 43 irradiates the laser S toward the upper surface 51 of the first calibration plate 5 . FIG. 5 shows this state. In short, the distance between the upper surface 51 of the first calibration plate 5 and the non-contact displacement gauge 43 is measured based on the detection signal of the non-contact displacement gauge 43 .

After the distance indicating the position of the upper surface 51 of the first calibration plate 5 is measured by the non-contact displacement gauge 43 in this way, the tip of the rod 22 is temporarily moved to a height equal to or greater than the thickness of the second calibration plate 6. lift.

Subsequently, in step S<b>15 , the second calibration plate 6 is installed on the upper surface 51 of the first calibration plate 5 . Then, the tip of the rod 22 is lowered and passed through the hole 62 of the second calibration plate 6 to bring the tip of the rod 22 into contact with the upper surface 51 of the first calibration plate 5 .

In step S<b>16 , the non-contact displacement gauge 43 irradiates the laser S toward the upper surface 61 of the second calibration plate 6 . FIG. 6 shows this state. In short, the distance between the upper surface 61 of the second calibration plate 6 and the non-contact displacement gauge 43 is measured by the detection signal of the non-contact displacement gauge 43 .

When the distance indicating the position of the upper surface 61 of the second calibration plate 6 is measured by the non-contact displacement meter 43 in this way, the displacement is calculated from the difference from the position of the upper surface 51 of the first calibration plate 5 measured in step S14. is calculated. This displacement is the result of measurement by the displacement measuring section.

Therefore, in step S17, the displacement measuring section is calibrated so that the displacement calculated from the measurement result of the non-contact displacement meter 43 is the same as the known thickness of the second calibration plate 6. FIG.

In the method for calibrating the ground investigation measuring device of the first embodiment configured as described above, the first calibration plate 5 is installed on the base portion 24 of the penetration tester 2, and the first displacement measuring portion (non-contact displacement meter 43), the second calibration plate 6 having a known thickness is placed on the first calibration plate 5, and the non-contact displacement gauge 43 performs measurement again. Then, the displacement measurement unit is calibrated based on the measurement results of the non-contact displacement meter 43 twice.

In this way, the plate-shaped simple first calibration plate 5 and the second calibration plate 6 are installed in order on the pedestal portion 24 of the penetration tester 2, and measurement is performed by the non-contact displacement gauge 43. You can easily calibrate it.

For this reason, it is possible to repeatedly perform calibration at an arbitrary timing such as before or during the test, so that it is possible to efficiently perform highly accurate measurement.
Other configurations and effects are substantially the same as those of the above-described embodiment, so description thereof will be omitted.

Although the embodiments of the present invention have been described in detail above with reference to the drawings, specific configurations are not limited to these embodiments or examples, and design modifications that do not deviate from the gist of the present invention are possible. are included in the present invention.

For example, in the above-described embodiment and Example 1, the measuring device 4 including the load measuring unit composed of the strain gauge 42 and the displacement measuring unit composed of the non-contact displacement gauge 43 is used as an example of the ground investigation measuring device. has been described, but it is not limited to this. The load measuring section may be configured by a load cell, and the displacement measuring section may be configured by a potentiometer type displacement meter.

In the first embodiment, the second calibration plate 6 having holes 62 through which the rods 22 pass is described as an example. However, the second calibration plate is not limited to this. It may be of a size that is installed only at the reflecting point of the laser S of the displacement gauge 43 . In this case, the step of once raising the rod 22 after measuring the upper surface 51 of the first calibration plate 5 can be omitted.

Also, in the first embodiment, the method for calibrating the laser-type displacement measuring unit attached to the rod 22 has been described, but the method is not limited to this. For example, when a potentiometer-type displacement meter that directly measures the amount of descent of the rod 22 is used as the displacement measuring unit, the tip of the rod 22 is brought into contact with the upper surface 51 of the first calibration plate 5 for measurement, and then the second Displacement corresponding to the thickness of the second calibration plate 6 was measured by contacting the top surface 61 of the second calibration plate 6 placed on the first calibration plate 5 with the tip of the rod 22 . It will be.

2: Penetration tester 22: Rod 24: Pedestal 25: Weight 3: Exciter 4: Measuring device (measuring device for ground investigation)
42: strain gauge (load measuring unit)
43: non-contact displacement meter (displacement measurement unit)
5: First calibration plate 51: Upper surface 6: Second calibration plate 61: Upper surface G: Target ground

Claims (2)

A method for calibrating a ground survey measuring device attached to a penetration tester that penetrates a rod into the ground when surveying the target ground,
The penetration tester includes a pedestal portion having an open portion for penetrating the rod into the target ground, and a weight portion and a vibrator for applying a load to the upper end of the rod,
installing a first calibration plate on the pedestal so as to block at least a path through which the rod passes through the open portion;
contacting the tip of the rod with the first calibration plate;
A step of loading a known load based on the weight and the vibrator on the rod and performing measurement by the load measuring unit of the measuring device for ground investigation;
A method for calibrating a measuring device for ground investigation, comprising a step of performing calibration based on the measurement result of the load measuring unit and the known load. A method for calibrating a ground survey measuring device attached to a penetration tester that penetrates a rod into the ground when surveying the target ground,
The penetration tester comprises a pedestal having an opening for penetrating the rod into the target ground,
installing a first calibration plate on the pedestal so as to block at least a path through which the rod passes through the open portion;
contacting the tip of the rod with the first calibration plate;
a step of performing measurement with the upper surface of the first calibration plate as a reference by the displacement measuring unit of the ground investigation measuring device;
placing a second calibration plate of known thickness on the first calibration plate;
a step of measuring the upper surface of the second calibration plate with the displacement measuring unit as a reference;
A method for calibrating a ground investigation measuring device, comprising a step of performing calibration based on the measurement result of the displacement measuring unit and the thickness of the second calibration plate.

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